This invention relates generally to soldering devices and more particularly to solder tips and a dual purpose device for both applying and removing solder.
FIG. 1 shows a prior art "trigger activated" solder gun 10 having a main housing 11. By pressing a trigger 12, electrical power from a coil inside solder gun 10 (not shown) passes from terminal 14 through a solder tip 16 and then back through terminal 18. The resistance of solder tip 16 creates heat that is used to melt solder onto various articles.
For example, solder is used to electrically couple a lead on an integrated circuit (IC) to an electrical connection on a printed circuit board. Electric solder guns and their operation are well known to those skilled in the art and are, therefore, not described in detail.
Solder tip 16, however, is too wide to be easily placed in constricted locations and to apply solder with high precision. Solder tip 16 is so wide that front end 20 can easily touch two adjacent leads of an IC at the same time inadvertently soldering the leads together. In addition, opposite ends 19 and 21 of solder tip 16 are spaced relatively far apart when inserted into terminals 14 and 18, respectively. Because the ends 19 and 21 are spread apart, the overall structure of solder tip 16 is not very strong. Thus, a strong force exerted on solder tip 16 will cause the tip to bend or possibly break.
Solder tip 16 is also difficult to replace. For example, to attach solder tip 16 in solder gun 10, the ends 19 and 21 of solder tip 16 are inserted in terminals 14 and 18. Two screws 15 are then screwed into terminals 14 and 18 clamping onto the solder tip ends 19 and 21. To replace solder tip 16, screws 15 are unscrewed from terminals 14 and 18, solder tip 16 removed, and a second solder tip inserted. Screws 15 are then retightened into terminals 14 and 18. Thus, the present method for replacing solder tips is both difficult and time consuming.
The temperature of solder tips varies according to the amount of drive current passing through the solder tip and according to the type of materials that come into contact with the solder tip. For example, a material coming into contact with solder tip 16 can act as a heat sink, directing heat away from the solder tip. Continuous changes in solder tip temperature shorten solder tip operating life and make it difficult to maintain a consistent temperature sufficient to melt solder.
U.S. Pat. No. 3,883,716 to Fortune describes an electronic circuit for maintaining a constant temperature at the tip of a soldering device. However, solder tip temperature is controlled by using complex electronic circuitry. The circuitry increases manufacturing costs and is susceptible to electrical malfunctions.
To remove existing solder joints, a special device known as a solder sucker is used to first melt and then ingest the molten solder. FIG. 8 shows a prior art solder sucker 22. The solder sucker 22 includes a handle 24 coupled by a mounting base 26 to a heating section 28. A heating element 30 is located in heating section 28 and is joined at a front end to a hollow solder tip 32.
A plunger 34 is detachably mounted to the top of handle 24. The plunger 74 includes a plunger rod 36 that extends a spring (not shown) inside the plunger 34 lockable into a "cocked" position as shown in FIG. 8. A locking mechanism 44 at a back end of plunger 34 latches to the plunger rod 36 holding the plunger rod 36 in the "cocked" position. A hollow pipe 38 extends from a vacuum hole (not shown) at the front end of plunger 34, through heating section 28 and to a cavity 40 in the hollow solder tip 32. Solder tip 32 becomes hot when heating element 30 is energized via an external power supply (not shown). The power supply is connected to heating element 30 by an electrical cord 42 as shown in phantom inside the handle 24.
To remove existing solder joints between two devices, plunger 34 is first locked into the "cocked" position as shown in FIG. 8. After solder tip 32 reaches a sufficient temperature, it is pressed against a solder joint melting the solder joint. A button 43 in locking mechanism 44 is then depressed releasing the plunger rod 36 from the cocked position. Plunger rod 36 is pulled in a backward direction by a spring (not shown) creating a vacuum inside pipe 38. The vacuum pulls molten solder through solder tip 32 and pipe 38 into a cavity inside plunger 34.
The solder sucker 22 is used in coordination with a solder gun. For example, a solder gun is used to apply solder to an electrical terminal. When solder is deposited in the wrong location, a soldering iron (see FIG. 1) must be carefully set down to prevent accidental melting or burning. The solder sucker 22 is then picked up and the hollow solder tip 32 pressed against the unwanted solder joint. The solder joint is then remelted and the solder sucker activated to remove the molten solder. The solder sucker is then placed back into its previous location and the solder iron again picked up to continue the soldering process.
Using both a solder iron and a solder sucker is expensive and wastes energy since two separate devices have to be continuously heated at the same time. Using two soldering devices is also time consuming and awkward since both devices are continuously picked up and laid down. Because it takes a substantial amount of time to switch between the solder iron and the solder sucker, when solder is mislaid, the solder has more time to cool and harden. Thus, more time is required to remelt and remove the mislaid solder.
It is also awkward to both hold the solder sucker and activate the suction mechanism at the same time. For example, after a solder joint has been deposited in the wrong location, hollow solder tip 32 must be carefully replaced at the exact location of the solder joint. The trigger mechanism is then activated by pressing the button 43.
U.S. Pat. No. 4,023,724 to Wakita et al shows a solder gun with a trigger activated suction pump that creates a vacuum in a solder removing bit. Molten solder is removed by pulling solder through the solder bit. Because the solder bit remains heated, energy is also wasted when the solder bit is not actually melting solder. It is also more likely that someone or something will get burned since the solder bit remains heated when not in use.
Accordingly, a need remains for a low cost device for quickly and accurately applying and removing solder with an easy to attach solder tip that is resistent to bending while at the same time maintaining a constant temperature over a wide range of operating conditions.